Unreal

Unreal takes place about 200 years from now. you are a prisoner aboard the UMS Vortex Rikers. Your so-called home crashes on an unknown planet, and you must find a way to escape. You fight various creatures on the planet, and use various weapons, some Terran (of Earth), and some of the Skaarj, the primary enemy species.

Unreal: Return to Na Pali is an expansion pack to Unreal and the original release of the pack required the full version of Unreal to install and play. The game takes place after the events in Unreal and puts you back on the planet Na Pali to find another crashed spacecraft.

Although Unreal is old it's still a brilliant game. One the best FPS created, in my opinion. You should definitely give it a try if you hadn't yet. But you should keep in mind that unlike most modern First Person Shooters it's long and difficult.